This invention relates to a dielectric liquid impregnant for electrical devices and more particularly to an electrical capacitor utilizing an improved non-toxic dielectric liquid impregnant theretofore.
Liquid impregnants for electrical capacitors should have a high dielectric constant, maintain a low dissipation factor, and be compatible with the other materials utilized in capacitor structure. At the same time, the impregnant must withstand elevated and fluctuating temperature, pressure, and voltage stress conditions with excellent electrical characteristics for a long operative life of the capacitor.
The polychlorinated biphenyls as capacitor impregnants meet these requirements and they were eminently satisfactory for several decades. The polychlorinated biphenyls are broadly referred to as PCBs. The polychlorinated bihpenyls have recently been associated with ecological problems, restrictive use limitations, and rising costs. These problems have spurred the search for a suitable non-toxic replacement capacitor impregnant which would have some advantageous impregnant characteristics comparable to those of the chlorinated diphenyls, and still provide outstanding electrical and compatibility performance with the two most important present day capacitor solid dielectrics, paper and polypropylene.
In the search of a non-toxic liquid impregnant, consideration must also be given to gas absorbing properties and offensive odor which may evolve when the capacitor is used for prolonged periods at elevated temperatures. Good gas absorbant properties prolong capacitor life.